Such a forgery wouldn't fool intensive forensic analysis. It's one thing to get a 48 year old printer, it's another to come up with 48 year old paper, and 48 year old ink. Even if you managed to do that, and get it to all go together properly, it would be possible to determine that the ink had been applied to the paper recently, rather than 48 years ago.
The story was that they were working the fake BC over for an extended period of time with ultraviolet radiation and moisture. Again, I don’t know if this is true.
The problem with forensic analysis is to come up with experts you can trust. Now, who could you trust to analyze Obama’s birth certificate? The FBI? No doubt experts could be found who were not already suborned, but then other experts would be found to testify that it was real.
I agree with you that it’s likely impossible to make an analysis-proof forgery, but we’re in a position where finding impartial analysis is difficult, and getting the word out is also difficult.
So, we see how this plays out.